You can't leave the Pentagon or the NSA without authenticating on exit. At least, I couldn't exit.
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Robert David GrahamSep 24 '11 at 0:15

1

It is common on airports after you leave a flight from another country
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Hendrik Brummermann♦Sep 24 '11 at 7:33

good job posting that on a public forum with your full name
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devnul3Sep 29 '11 at 20:14

@Hendrik, but that's more about authenticating on entry to the country, not about leaving the airplane...
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AviD♦Oct 7 '11 at 6:54

@AviD, yes, of course. But it does have similar issues, most notable the fire emergency. And there is a good solution to that issue: The checks are done by humans who can react in case of fire.
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Hendrik Brummermann♦Oct 7 '11 at 6:56

3 Answers
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Some places do, but most do not from the viewpoint that they are only concerned about who is getting into the place.

Places I've worked where authenticating those leaving was the norm included:

A manufacturing facility, who was also checking bags and pockets to detect if you were trying to steal product. Who got checked was randomly determined by the system. This made it so that you could not collaborate with guards to smuggle out loot.

A coal mine, where knowing who was still inside the mine during fires/emergencies was essential to knowing who still needs to be rescued. A side effect of this was that it made clocking in/out for friends impossible.

One company was concerned about people leaving a swipe card on top of the reader, so before a card could be used to re-enter the place, it had to be used to swipe out.

One place that used swipe cards for leaving was a variation of time clock for employees. Some were 2-swipe employees ("in" in the morning, and "out" when leaving at night), and some were 4-swipe employees (in addition to "in" in the morning and "out" at night, you were expected to swipe in and out for lunch). The 2-swipe folks were expected to work 50 hour weeks and were paid a little more than 4-swipe employees. This company was regulated as a bank and had the side effect that the 2-swipe employees always took 2+ hour lunches.

Most jurisdictions require that doors unlock automatically in the event of an emergency such as fire or even power outage. Again, truly secure buildings will move security personnel into positions to try and monitor peoples movements and make sure nothing bad happens.

There may be some potential for liability, if this was applied to facilities open to members of the general public. It's one thing to do it in a national-security facility, or apply this policy to employees, but it would be another thing to do it to random members of the public.

What if I enter a library or movie theater, decide I want to leave, and refuse to show ID on the way out? Are they going to physically bar me from leaving, under threat of violence? If so, that sounds a lot like false imprisonment -- a felony. It may also be battery (if they touch me) and/or assault (if they threaten me). On the other hand, if I decide to leave and they don't bar the path, then that's a big gaping loophole that raises questions about the purpose of "requiring" (but not really requiring) authentication on exit.

+1 @D.W.: Nice analysis. It's interesting how logically it doesn't make sense, meaning if you agree something to enter a build, how/why those same measure if know on entering wouldn't be legal on exit.
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blundersSep 26 '11 at 4:08